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Pos-option

Pos-option-case

Case macro for the different kinds of pos-option structures.

This is an fty sum-type case macro, typically introduced by fty::defflexsum or fty::deftagsum. It allows you to safely check the type of a pos-option structure, or to split into cases based on its type.

Short Form

In its short form, pos-option-case allows you to safely check the type of a pos-option structure. For example:

(pos-option-case x :none)

can be used to determine whether x is a none instead of some other kind of pos-option structure.

Long Form

In its longer form, pos-option-case allows you to split into cases based on the kind of structure you are looking at. A typical example would be:

(pos-option-case x
  :none ...
  :some ...)

It is also possible to consolidate ``uninteresting'' cases using :otherwise.

For convenience, the case macro automatically binds the fields of x for you, as appropriate for each case. That is, in the :none case, you can use fty::defprod-style foo.bar style accessors for x without having to explicitly add a none b* binder.